Patient transport method and apparatus

ABSTRACT

A transport method and apparatus is provided capable of reducing the accelerations encountered by an item or patient due to an external energy input to the transport device, by utilizing an active control system adapted to input a second energy to offset the effect of the external energy input.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a transport device andmethods, and particularly to reducing the effects and damage to items orpatients being transported as a result of certain energy inputs to thetransport device and resulting acceleration-related inputs to thepatient or item.

BACKGROUND OF THE INVENTION

Patient transport devices, often referred to as gurneys, stretchers, andthe like, have long been used to transport people having injuries fromone place to another, such as from an accident site to a hospital, orfrom hospital to hospital, etc. In addition to being themselves mobile,many patient transport devices may be adapted for use with a number ofdifferent transport vehicles, including ambulances, airplanes,helicopters, snow machines, and the like. When these vehicles aretransporting patients from one location to another, they inevitablyencounter disturbances such as bumps, potholes, turbulence, or otherinconsistencies in the transport medium, which in turn causes a suddenchange in position of the patient transport device. This abrupt changein position is transmitted to the patient, and can cause the patient tobe subject to accelerations in various directions.

The magnitude of these external energy inputs and the resultingaccelerations of the patient in different directions can have a severeand oftentimes detrimental impact on the patient being transported,particularly if the patient has head, neck, and/or spinal trauma, forexample. Any undue energy input cannot only further aggravate anexisting injury, but may ultimately result in death.

Another particularly susceptible category of patients are neonatalpatients. Oftentimes being several weeks if not months premature, thebiological systems within the neonatal patient, particularly thevascular system, has not fully developed and is extremely susceptible todamage. Even the smallest amount of vibrations and accelerationstransmitted to the neonatal patients through the patient transportdevice during transfer can have traumatic impacts. One serious concern,but not the only serious concern, is intraventricular hemorrhage, whichis where blood vessels in the brain rupture. Because the blood vesselsin the brain of neonatal patients are underdeveloped (i.e., very thinand not prepared for significant stress), the vibrations and theaccelerations of the patient as a result of the vibrations may cause theblood flowing through those vessels to be inclined to suddenly stopand/or change directions. Since this is not possible due to thecontinuous flow of blood through the system, an outward pressure isapplied to the underdeveloped vessel causing them to fatigue and/orrupture.

Current patient transport devices often have a number of inherentpassive energy and vibration absorption systems, such as a mattress,rubber in the wheels of the transport device, and when a vehicle isused, for example, the vehicle's suspension. Some patient transportdevices may even have additional passive systems, such as shockabsorption devices to further absorb various energy inputs. Thesedevices may not provide an acceptable energy and vibration absorptioncapability for the susceptible patients described above. While thepassive systems may ultimately absorb external energy inputs andvibrations, they are often too slow, may initially amplify theaccelerations resulting from certain energy inputs, and cannotadequately attenuate the acceleration encountered by the patient.

Accordingly, it is desirable to develop a patient transport device thatsomewhat decouples the patient from the transport device such that theexternal energy inputs, such as vibrations, impulse inputs, and stepinputs encountered by a patient transport device, will be minimized andany accelerations of the patient as a result will be reduced so as toreduce the creation and/or aggravation of existing injuries.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings. To facilitate this description, like reference numeralsdesignate like structural elements. Embodiments of the invention areillustrated by way of example and not by way of limitation in thefigures of the accompanying drawings.

FIG. 1 illustrates a perspective view of a patient transport device inaccordance with an embodiment of the present invention;

FIGS. 2A-2D illustrate a transport device responding to an externalenergy input in accordance with an embodiment of the present invention;

FIGS. 3A and 3B illustrate graphs comparing test results of variouspatient transport devices with patient transport devices in accordancewith embodiments of the present invention;

FIG. 4 illustrates a control block diagram of a transport device systemresponse in accordance with an embodiment of the present invention;

FIG. 5 illustrates a plan view of a patient transport device inaccordance with an embodiment of the present invention;

FIG. 6 illustrates a plan view of a patient transport device inaccordance with an embodiment of the present invention;

FIG. 7 illustrates a plan view of a patient transport device inaccordance with an embodiment of the present invention; and

FIG. 8 illustrates a block diagram of a method of reducing accelerationsof a patient being transported in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the invention may be practiced. It isto be understood that other embodiments may be utilized and structuralor logical changes may be made without departing from the scope of thepresent invention. Therefore, the following detailed description is notto be taken in a limiting sense, and the scope of embodiments inaccordance with the present invention is defined by the appended claimsand their equivalents.

Embodiments of the present invention relate to the reduction of externalenergy inputs, such as vibrations, step, and impulse inputs, that aretransmitted to something being transported, such as a patient, throughthe transport device, by implementing an Active Control System (ACS).The ACS may include both passive suspension components and an activecontroller adapted to input energy into the system, wherein they work incooperation to reduce the impact of external energy inputs on a patientor item being transported. Embodiments in accordance of the presentinvention may include a controller that may input a force in a directionrequired to cause the patient support to track back to a position thatis a predetermined distance away from a portion of the frame of thepatient transport device. This action may have the overall effect ofreducing the acceleration of a patient as a result of the externalenergy input. Embodiments of the present invention may include alteringthe magnitude and direction of the force input by the controller basedon the direction and magnitude of the external energy input.

Active control systems in accordance with embodiments of the presentinvention may be configured to reduce the amount and/or effect of anexternal energy input to the transport device that may be transmitted tothe item or patient being transported. A number of different externalenergy inputs may be encountered, including vibrations (high-frequency,low-magnitude input) that may be caused for example rolling a gurneyover rough surfaces such as aggregate, elevator threshold, and the like.Another external energy input may be caused by a step input, which mayoccur when an ambulance hits a curb, for example, such that the overallposition of the patient transport device steps up or down from a firstelevation to a second elevation. Yet another external energy input maybe caused by an impulse input, which may result from an ambulancehitting a speed bump or pothole, for example, where the patienttransport device is temporarily displaced from a first elevation to asecond elevation and then returns to the first elevation.

FIG. 1 illustrates a perspective view of a patient transport device inaccordance with an embodiment of the present invention. A patienttransport device 10 may include a support reference 12, such as asupport deck, that may be removably coupled to the patient transportdevice 10. In one embodiment, the support reference 12 may be coupled toand/or part of frame 14 that may be adapted for transport via wheels 16.A patient support 13 may be dynamically coupled to the support reference12 through an ACS 21. In the case of neonatal transport, for example, anincubator 15 may be coupled to the patient support 13, and the incubatorcontrols 17 and support components 18 may also be coupled to the supportreference 12. The support reference may generally be any portion of apatient transport device that will be susceptible to generallyuncompensated positional changes as a direct result of an externalenergy input and that acts as a reference point for which the patientsupport can move relative to.

In one embodiment, the ACS 21 may include guide members 30 configured topositionally couple patient support 13 to support reference 12 and allowlimited movement in one or more desired directions. While the degrees ofmovement may be enabled as desired, in the illustrated embodiment, guidemembers 30 are configured to allow for linear movement of the patientsupport 13 vertically with respect to the substantially horizontalposition of the support reference 12.

The ACS 21 may also include one or more passive suspension devices 18actively coupled between the patient support 13 and the supportreference 12. Passive suspension devices 18 may include a spring 32configured to absorb energy stemming from the positional change of thesupport reference 12 caused by the external energy input. Passivesuspension devices 18 may also include one or more dampeners 34configured to dampen the absorption and/or release of energy throughsprings 32. While the passive suspension devices illustrated showseparate components, such devices may be a single component, and mayinclude other spring mechanisms such as elastomers.

Given an external energy input to the support reference 12, which may becaused, for example, by the patient transport device 10 crossing asliding door threshold or encountering a curb, the magnitude of theenergy input may be initially at least partially absorbed by the one ormore passive suspension devices 18, and thus result in a reduced energyinput being conveyed to the patient support 13. This may in part resultin a decrease in the position, velocity, and/or acceleration of thepatient support 12 as a result. Passive suspension devices 18 mayinclude a variety of energy absorption and dampening devices and/orvibration/shock absorption devices, including, but not limited to,springs and dampers, electromagnetic fields, pneumatic systems, and thelike.

The ACS 21 may also include a force generator 20 controllably coupledbetween the patient support 13 and the support reference 12. Forcegenerator 20 may be adapted to input a second energy or force into thesystem aimed at offsetting some or all of the effects (positional,velocity, and acceleration) on the patient support 13 that could resultdue to the external energy input. Input of the second energy by forcegenerator 20 may help to counteract the positional movement of thepatient support 13, and in turn reduce the acceleration observed by thepatient as a result of the external energy input. The direction andmagnitude of the second energy input may be varied as required tominimize the positional change of the patient support with respect tothe support reference 12.

As illustrated in FIGS. 2A-2D, the direction and magnitude of the secondenergy input may vary depending on the required dynamic response. Forexample, the second energy input may be at time in a direction oppositeto the direction the support reference is traveling, and at times in thesame direction as the movement of the support reference. FIG. 2Aillustrates support reference 12 may be at a position P1 and the patientsupport 13 at a position of P1′ prior to any external energy input. Thedistance between P1 and P1′ may be a desired static separation distanceD1.

When an external energy is applied to the system, a step input in theillustrated case of FIG. 2B, the support reference 12 will move from afirst position P1 to a second position P2. Due to the passive suspensionof the ACS, the patient support 13 may substantially remain at P1′,thereby resulting in a separation distance of D2. At that time, thepatient support 13 may be considered as traveling with a negativevelocity with respect to the support reference 12. To counteract thenegative velocity, the force generator may input a second energy F1 inan upward direction, thereby urging patient support 13 upward in anattempt to urge D2 to equal D1.

Once the energy stored in the springs of the passive suspensioncomponents, along with the second energy input F1, begins to move thepatient support 13 vertically upward with respect to the supportreference 12, a positive velocity of the patient support will result.The patient support may also move from P1′ to P2″, resulting in aseparation distance D3, as illustrated in FIG. 2C. To counteract thepositive velocity, force generator may input a second energy F2 in adownward direction, directly opposing the movement of the patientsupport in an upward direction, until the velocity of the patientsupport again becomes negative.

This cycle may repeat until the velocity of the patient support 13 issubstantially zero with respect to the support reference 12 and theseparation distance is substantially back to the static distance of D1.As shown by FIG. 2D, the separation distance of support reference 12with respect to patient support 13 is back to D1, where the supportreference is at the new elevation P2 as a result of the step input andthe patient support is at P2′″. The same process may occur when othersources of external energy are encountered by the system, including, butnot limited to step inputs, vibrations, and the like.

FIGS. 3A & 3B show a comparison of the dynamic response (position andacceleration) of a patient support to a step input in uncompensated,passively compensated, and actively compensated systems, with 3Arepresenting position response comparison and 3B representingacceleration response comparisons. Lines 44 (position) & 44′(acceleration) are the system response of the uncompensated system; thatis, the system with virtually no energy absorption components. Lines 42& 42′ show the system response of the passively controlled system; thatis, the system without the internal energy device, or force generator.Lines 40 & 40′ show the system response using the ACS in accordance withembodiments of the present invention. These figures illustrate a typicalresponse of the patient support as the result of the movementillustrated in FIGS. 2A through 2D, when the step input is, for example,0.1 meters.

As can be seen from FIGS. 3A and 3B, the ACS in accordance withembodiments of the present invention can significantly reduce therelative positional movement and the accelerations that the patientsupport experiences due to an external input to the system, which inturn minimizes the accelerations transmitted to a patient beingtransferred. It was found in both theoretical modeling and in thetesting of a proof of concept device, there was a reduction of the peakacceleration of the patient support (thus the patient) fromapproximately 13 m/s2 (uncompensated) to approximately 2 m/s2. As can beseen in the comparison charts, not only is the peak acceleration less inthe ACS, the acceleration encountered by the patient attenuates in ashorter time interval. It was also found in the tests that there was anaverage overall reduction in the frequency weighted RMS accelerationseen by the patient across a range of 0 to 10 Hz from 0.67 m/s2 to 0.11m/s2. It was further found that use of ACS in accordance with thepresent invention resulted in close to an 85% reduction in accelerationstransmitted to the patient over the relative to existing systems.

Testing was also conducted where the energy input was the result of animpulse input, such as hitting a speed bump in an ambulance orturbulence in an airplane. Again, there was found to be a significantreduction in the position movement and acceleration of the patient.Likewise, the accelerations attenuated more rapidly than current systemsnot using ACS.

The force generator 20 may be configured in a variety of ways that may,allow for the controllable supply of a second energy input into thesystem. In one embodiment, for example, one or more rotary motors may beused in conjunction with a rack and pinion system to control themagnitude and direction of the second energy input, as shown in FIG. 1.In another embodiment, one or more linear motors, such as an MTS system2000 series motor, may be coupled between the support reference and thepatient support, and adapted to generate the second energy input in adesired direction and a desired magnitude. Other sources of linearmotion generation and control may be used, which include, but are notlimited to electromagnetic field manipulators, pneumatic and/orhydraulically controlled actuators, and the like.

Embodiments of the present invention may also include sensors 19 thatmay be adapted to sense the direction and magnitude of a responsecharacteristic of the patient support 13 as a result of the externalenergy input. Sensor 19 may be in communication with a controller 23adapted to apply a control law based on an input from sensor 19.Controller 23 may send a signal to force generator 20, such that theforce generator may input a second energy of a magnitude of anddirection appropriate to offset some of the effects of the externalenergy input, and ultimately reduce the acceleration of the patientsupport and, as a result, the patient. Sensor 19 may be, for example, aposition, velocity, and/or acceleration based sensor.

The ACS in accordance with embodiments of the present invention may be aclosed loop system employing negative feedback. Generally, when there isa disturbance to the system, e.g., an external energy input, the systemdynamically responds, the response is sensed/measured, the forcegenerator is sent a signal and the system responds dynamically to thesecond energy input, thus changing the sensed/measured characteristic.The total system response is again measured by the sensor and the forcegenerator is again sent a signal causing the system to again respond.This is repeated until the system returns to an equilibrium state, e.g.,zero input to the sensor measuring the response characteristic.

In one embodiment, the magnitude and direction of the second energyinput may be determined and controlled via a negative feedback controlloop, an example of which is illustrated in FIG. 4 in block diagramform. The overall system response G_(SYS) (i.e., position, velocity, andacceleration) of the patient transport device may be characterized bythe summation of the system response to the external energy input R,referred to as G_(SYS) _(—) _(R) and the system response to the secondenergy input F (i.e., by the force generator), referred to as G_(SYS)_(—) _(F). In terms of the measured system response characteristic orvariable (e.g., position, velocity, and acceleration), overall systemresponse characteristic Y₁ will be equal to the sum of Y_(R), which isthe system characteristic as a result of the external energy input R,and Y_(F), which is the system characteristic as a result of the secondenergy input F.

Sensor 19 may be adapted to sense Y1 and generate a representativesignal S_(V), such as a voltage or current that characterizes theresponse characteristic being sensed. A controller 23 may be inelectrical communication with the sensor 19 and adapted to receive thesensor signal S_(V). The controller may compare the sensor signal S_(V)to a reference point to determine the variation of the responsecharacteristic from a desired state. For example, the reference pointmay be a specific position of the patient support relative to the restof the transport device; or a zero velocity indicating that the patientsupport is not moving relative to the rest of the transport device. Thecontroller may then process the sensor signal using a predeterminedcontrol law, and generate a control signal Sc. The force generator 20,which may be in electrical communication with the controller, may beadapted to receive the control signal S_(C), and generate a secondenergy input F. Second energy input F will result in the system responseG_(SYS) _(—) _(F), and generate Y_(F) as a result.

In one embodiment of the present invention, sensor 19 may be avelocity-based sensor adapted to measure the velocity of the patientsupport 13. The velocity sensor may be may be coupled to the controller,such that when a negative velocity is sensed, for example, thecontroller 17 generates a control signal to the force generator 20 togenerate a force of a certain magnitude in positive direction to offsetthe negative velocity. The sensor may continue to measure the velocityof the patient support and generate sensor signals representing theresponse characteristic.

Periodic generation of sensor signals and thus generation of controlsignals may cause the force generator to variably alter the directionand magnitude of the second energy input until the velocity of thepatient support is substantially zero. This periodic measurement ofsensor signals and subsequent generation of appropriate control signalsthat are in turn sent to the force generator creates a feedback loop.This feedback loop constantly adjusts the force generated as theresponse characteristic changes over time. The control law is formulatedto return the system to its original state (i.e., the state prior to theexternal input Y_(R) acting on the system) as quickly as possible whileminimizing the accelerations transmitted to the patient support as wellas the overall movement of the system. This may in turn result inquicker attenuation of the accelerations of the patient support thanwould normally occur with only passive suspension components.

In one embodiment, where the sensor is a position sensor, and theexternal energy input is a step input directed to the patient transportdevice (e.g., hitting a curb) the support reference dynamically respondsby raising to a second position. The position sensor will sense suchsecond position and generate a sensor signal representative of the newposition. The controller may process the signal using a control law andgenerate a corresponding control signal that will cause the forcegenerator to provide a second energy input in the system to try andmaintain a desired distance between the support reference and thepatient support, while minimizing the relative velocity and overallacceleration of the patient support.

FIG. 5 illustrates a plan view of a patient transport device 200 inaccordance with an embodiment of the present invention. Incubator 215may be coupled to patient support 213, which in turn may be coupled tosupport reference 212 through an ACS 221 in accordance with embodimentsof the present invention. ACS 221 may be in electrical communicationwith sensor 219 and controller 223. Incubator controls 217 and supportcomponents 218 may also be coupled to the support reference 212. Supportreference 212 may be removably coupled to a frame 214, which may beadapted for movement on wheels 216. Support reference 214 may be removedalong with patient support 213, incubator 215, ACS 221, sensor 219,controller 223, and support controls and components 217 and 218, andloaded into a transport vehicle, such as a helicopter. In such a case,the ACS 221 may continue to operate to reduce effects of external energyinputs to the patient transport device through the inconsistenciesencountered by the transport vehicle on the patient support and thus thepatient.

FIGS. 6 and 7 illustrate plan views of patient transport devices inaccordance with embodiments of the present invention. Patient transportdevices 310A and 310B may be adapted for transporting patients of allsizes. Both may include a support reference 314 and a patient support312. A removable interposer 315 may be disposed between patient and thepatient support 312. Interposer 315 may be rigid enough to support thepatient, such as a backboard, and adapted to allow personnel to move thepatient to and from the patient support 312. In other embodiments, theinterposer may be a comfort item, such as a mattress. The patienttransport devices 310A and 310B may include an ACS 321A and 321Bconfigured to reduce the effects of an external energy input to thepatient, as a result of position, velocity and/or acceleration changes.

The ACS 321A of FIG. 6 may include passive suspension components 318Acoupled between the support reference 312 and the patient support 314,and a force generator 320A configured to input a second energy into thesystem. Force generator 320A may include a rotary motor that may becoupled to the support reference 312 and patient support 314 through arack and pinion system 321A. The rotary motor and the rack and pinioncoupling may enable control of the linear movement of the supportreference 312 based on a control signal resulting from the sensorsignals of sensors 319.

FIG. 7 illustrates a similar patient transport device 310B, but may beadapted for larger and heavier patients. The ACS 321B may include aforce generator 320B coupled between the support reference 312 and thepatient support 314 in multiple areas through rack and pinionconnections 321B. Such a configuration may enable a greater degree oflocal control as well as support patients having greater mass.

FIG. 8 illustrates a block diagram of a method of reducing the effectsof external energy inputs observed by a patient during transport inaccordance with embodiments of the present invention. A patienttransport device may be provided that includes an ACS in accordance withembodiments of the present invention and which includes a sensor inelectrical communication with a controller that is in electricalcommunication with a force generator, and adapted to generate andcontrol linear motion of the patient support with respect to the supportreference (100). A response characteristic of the patient support deviceas a result of an external energy input may be sensed/measured (110). Asensor signal representative of the response characteristic may begenerated and sent to the controller (120). The controller may generateand send a control signal to the force generator that is representativeof a required amount of a second energy input (130). The force generatormay then input a second energy of a magnitude necessary to reduce theamount of the external energy input transmitted to a patient on thepatient transport device (140).

Embodiments of the present invention may be used with a variety ofdifferent patient transport device configurations, including thoseadapted for transport in vehicles configured for transportation over theroadways, such as ambulances, transportation via the airways, such ashelicopters and airplanes, and/or vehicles adapted for other surfacessuch as snow, rough terrain, and the like. Embodiments of the presentinvention may also be used with other transport devices, where theaccelerations transmitted to an item being transported need to bereduced.

The active control system in accordance with embodiments of the presentinvention may be operated by a power source that is portable (e.g.,battery powered) or may otherwise be adapted to interface withelectrical system on board the transport vehicle. Further, the ACS maybe adapted to run on either DC or AC systems.

Although certain embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent embodiments or implementations calculated toachieve the same purposes may be substituted for the embodiments shownand described without departing from the scope of the present invention.Those with skill in the art will readily appreciate that embodiments inaccordance with the present invention may be implemented in a very widevariety of ways. This application is intended to cover any adaptationsor variations of the embodiments discussed herein. Therefore, it ismanifestly intended that embodiments in accordance with the presentinvention be limited only by the claims and the equivalents thereof.

1. A patient transport device, comprising: a patient support; one ormore passive energy devices coupled to the patient support and adaptedto absorb at least a portion of an external energy input to the patienttransport device; and a force generator controllably coupled to thepatient support and configured to provide a second energy input into thedevice to reduce the effect of the external energy input on the patientsupport.
 2. The patient transport device of claim 1, wherein the forcegenerator is adapted to generate and control linear movement of thepatient support with respect to a support reference.
 3. The patienttransport device of claim 2, wherein the force generator includes anelectrically driven motor.
 4. The patient transport device of claim 3,wherein the motor is a linear motor coupled to the support reference andhaving an actuator coupled to the patient support.
 5. The patienttransport device of claim 3, wherein the motor is a rotary motor coupledto the support reference and is coupled to the patient support through arack and pinion interface.
 6. The patient transport device of claim 1,further comprising a sensor in electrical communication with the forcegenerator, the sensor adapted to detect a response characteristic of thepatient support to an external energy input, and adapted to generate asensor signal representative of the characteristic.
 7. The patienttransport device of claim 6, wherein the sensor is adapted to sense aselected one of the following response characteristics: position,velocity, acceleration, and force.
 8. The patient transport device ofclaim 6, further comprising a controller in electrical communicationwith the force generator and the sensor, the controller adapted toreceive the sensor signal and apply a control law to generate a controlsignal.
 9. The patient transport device of claim 8, wherein the forcegenerator is adapted to receive the control signal and generate thesecond energy input based thereon.
 10. The patient transport device ofclaim 8, wherein the sensor, controller, and force generator are part ofthe same component.
 11. The patient transport device of claim 1, whereinthe patient support is adapted to couple to an incubator for neonataltransport.
 12. The patient transport device of claim 1, wherein thepatient support is adapted to couple to a transport bed for juvenile andadult transport.
 13. The patient transport device of claim 1, furthercomprising a support reference removably coupled to a frame of thepatient transport device such that the patient support device may beremoved from the frame.
 14. The patient transport device of claim 1,wherein the force generator is adapted to dynamically generate thesecond energy input based on a negative feedback control loop.
 15. Amethod for reducing the effect of an external energy input to a patientduring transport, comprising: providing a patient transport devicehaving a patient support coupled to an active control system thatincludes a sensor in electrical communication with a controller that isin electrical communication with a force generator, the force generatoradapted to at least generate and control linear motion of the patientsupport; sensing a response characteristic of the patient support as aresult of the external energy input; sending a sensor signalrepresentative of the response characteristic to the controller;generating a control signal based on the sensor signal that isrepresentative of a second energy input required; sending the controlsignal to a force generator; and inputting a second energy into thepatient transport device to reduce the amount of the external energythat is transmitted to the patient support.
 16. The method of claim 15,wherein sensing a response characteristic includes sensing the positionof the patient support with respect to a support reference, and theinputting second energy input includes generating a force input of anamount and direction sufficient to cause the distance between thepatient support and the support reference to remain constant.
 17. Themethod of claim 15, wherein sensing a response characteristic includessensing either position, velocity, or acceleration of the patientsupport.
 18. The method of claim 15, wherein the sensing a responsecharacteristic includes sensing position, and further includesdetermining the velocity of the patient support.
 19. The method of claim15, wherein the second energy input is proportional to the position andvelocity of the patient support.
 20. A transport device adapted toreduce the impact of an external energy transmitted to the device on anitem being transported, comprising: a support member; one or morepassive energy devices coupled to the support member and adapted toabsorb at least a portion of the external energy; and a force generatorcontrollably coupled to the support member and configured to provide asecond energy input into the device to reduce the effect of the externalenergy input on the support member, the force generator being controlledthrough a feedback control loop.